If his name weren’t Derek Jeter, there might be cause for alarm. But it is Derek Jeter, so there is no alarm.

“Playing good defense involves a certain rhythm,” said Jeter after the Yankees’ 8-3 loss to Boston at the Stadium yesterday. “Right now, I don’t have any rhythm. I don’t feel good out there.”

That cost the Yankees and especially Mike Mussina in yesterday’s loss. With the score tied at 2-2 and runners on first and second and no one out in the top of the third, Scott Hatteberg hit a ground ball right at Jeter.

“I just missed it,” said Jeter, who added that he is not bothered by any of the ailments that plagued him throughout spring training. “No excuses.”

He appeared to stumble right before the ball hit his glove and it ricocheted into the outfield. The grounder, which should have been a double play, loaded the bases and kept the rally going. Shea Hillebrand followed with a two-run double and Mussina never recovered.

“Most of those runs should never have happened,” Jeter said. “Everything that happened in that inning is basically my fault. I’ve got to catch that.”

Lately, however, that’s been a problem for the shortstop. He has made four errors in 14 games this season. With the ex^^^^^^^^^^^^^^^^^^^^^^^^^pected troubles of new second baseman Alfonso Soriano, the middle of the Yankees’ infield isn’t looking very strong.

“It has nothing to do with him,” Jeter said. “I’m not making the plays.”

And he has a rather simple explanation for why he is going through this.

“When you think about slumps, everyone thinks of offensive slumps,” Jeter said. “But you can have them on defense, too. When you are in one, it seems like you get every ball on an in-between hop. Sometimes, you do that to yourself. That’s what I’m doing now.”

He did it again in the sixth. Hillenbrand hit a grounder to Jeter that seemed to be a perfect double-play ball. But Jeter dropped it and managed only to get the force at second.